The present invention relates to filter devices for the removal of radioactive contaminants from a gas stream, and more particularly to a device for adding filter material to such a filter device.
In recent years, there has been considerable activity in providing filtration equipment for nuclear power facilities. Typical nuclear filtration equipment includes gas treating or filter cells containing a filter material such as charcoal which cells are contained in a filter housing. A nuclear contaminated gas stream is routed into the filter housing through appropriate inlet apertures in the housing wall. Interior to the filter housing, the contaminated gas moves across and through the charcoal filled gas treating cells to remove the contaminants from the gas stream. After the gas stream has passed through the charcoal filled cells, the now clean gas exits the filter housing through appropriate outlet apertures in the housing wall and is routed away from the filter housing.
From time to time, as the charcoal in the filter cells becomes too contaminated for effective filtering it must be removed and disposed of, and the filter cells replenished with fresh charcoal.
The approaches to the problem of replenishing the filter cells with fresh charcoal have been varied.
One approach has been to form the filter cells as charcoal filter trays removably mounted in the filter housing. When the charcoal becomes contaminated, the filter housing is opened, the contaminated charcoal trays are removed and the charcoal somehow disposed of, and trays filled with fresh charcoal are inserted in their place. Some of the problems with this approach are that the filter housing must be opened thereby exposing the ambient or area surrounding the filter housing to radiation from the nuclear contaminants captured by the charcoal in the charcoal trays, and the trays of contaminated carbon must be handled in some manner during their removal and disposal with an inherent danger of exposing personnel and the ambient or area surrounding the filter housing to radiation from the nuclear contaminants captured by the charcoal in the trays.
Another approach has been to construct open topped fixed filter cells in a filter housing and provide sealable ports in the roof of the filter housing over and communicating with the interior of the filter cells. To replenish the filter cells with fresh carbon, the filter housing roof ports are opened, and fresh charcoal is introduced therethrough and into the filter cells. The charcoal could be introduced through the filter housing roof ports by means of a pipe having a discharge open end in communication with the port. Another means for introducing charcoal through the roof ports is to provide a hopper filled with fresh charcoal, which hopper can be mounted for movement over the roof of the filter housing. When the hopper is positioned over an open filter housing roof port, fresh charcoal is discharged through appropriate gates in its bottom side of the hopper to fall from the hopper downwardly through the open filter housing roof port into the filter cell there below. When one cell is filled, the hopper is moved to the next cell and the process repeated. One of the problems with this approach is that the filter housing must be opened thereby exposing the ambient or area surrounding the filter housing to radiation built up within the filter housing during the filtering operation as nuclear contaminated gas passes through the filter cells disposed therein. Another drawback is that an adequate amount of space must be provided over the filter housing roof to allow for the opening of the filter housing roof ports and the filling equipment, be it pipes, hoppers, or other means.
Yet another approach in a filter housing constructed with fixed open topped filter cells has been to provide a conduit having one open end which is horizontally disposed across the open tops of the filter cells within the filter housing. The conduit has downwardly facing apertures spaced along its length so that each of the spaced apertures is in registration with the open top of a different one of the filter cells. The open end of the conduit projects through one of the walls of the filter housing and is adapted to be connected to a filler pipe leading from a source of fresh charcoal located outside of the filter housing. Fresh charcoal is blown through the filler pipe from the source of fresh charcoal, and into the conduit through its open end. The fresh charcoal discharges downwardly out of the conduit through the apertures formed therein and falls downwardly through the tops of the filter cells and into the filter cells. It is desirable that the filter cells be overfilled to compensate for subsequent settling of the charcoal in the filters. In order to accomplish this overfilling with the above-discussed approach, a hill of charcoal is formed over each filter cell with the apex of the charcoal hill being beneath its respective conduit aperture and sides of the charcoal hill sloping downwardly toward the margins of the filter cell. A problem with this approach is that a possibility exists that there will be an inadequate amount of overfilling at the margins of the filter cells to adequately compensate for charcoal settling, thus, producing an area in the filter cell void of charcoal. Further, because the tops of the filter cells are open, some of the gas passing through the filter cells flows upwardly through the open top instead of from laterally front to back through the filter cell. Of course, the gas flowing through the open top of the filter cell must also be filtered. However, in the above-discussed approach, due to the uneven overfilling of the filter cells there is a possibility that there will be an insufficient amount of charcoal overfilling at the margins of each filter cell to adequately filter the gas passing upwardly through the open top of the filter cell. A further drawback is that an adequate amount of space over the top of the filter cells must be provided to form the hill of charcoal.